Al-Steel Resistance Spot Welding Patents: Leaders & Trends 2026
- Filing has cooled from its 2019 peak. 458 records in 2019 versus a -52% drop from 315 filings in 2021 to 152 in 2024, the last complete filing year.
- The field is not concentrated. The top 5 assignees hold just 5.3% of all 51,331 records, and the top 10 only 8.9% — a long tail dominates this space.
- Alloy and coating chemistry outweighs welding process claims. C22C alloy composition (10.2% of records) and C23C coatings (6.5%) each draw more filings than B23K welding itself (3.4%).
Filing growth compares 2021 (315 records) with 2024 (152) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 51,331 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Joining aluminium to steel by resistance spot welding sits at the intersection of dissimilar-metal metallurgy and welding process control. The dataset in scope spans 51,331 published records filed or published between 2015 and mid-2026, captured through claims and abstract language covering intermetallic compound thickness, electrode force, current schedules, cover plates, insert process variants, joint strength, cross-tension performance and corrosion behaviour at the weld interface.
Because a single record can carry multiple IPC classes, the technology composition below adds up to more than the record total — that is expected, not an error. Filing activity in the most recent one or two years is understated by design: publication typically lags filing by roughly 18 months, so 2025 and 2026 figures will keep rising as more applications publish.
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Filing trend and technology composition
Two views of the same 51,331-record dataset: filing activity by year, and the IPC subclasses that carry the claim density.
Filings rose to a 2019 peak, then declined
Annual filings climbed from 386 in 2017 to a peak of 458 in 2019. The clearest complete-year comparison is 2021 to 2024, where filings fell 52% from 315 to 152 — a real contraction, not an artefact of publication lag, since both years are fully published. Figures for 2025 and 2026 are still filling in and should not be read as a continued decline yet.
Alloy and coating chemistry lead welding process claims
C22C (alloys) appears in 10.2% of all records and C23C (coating and surface deposition) in 6.5%, both ahead of B23K (welding, soldering and brazing) at 3.4%. C22F non-ferrous treatment (3.9%), B32B laminates (3.1%), C25D electroplating (2.7%), C09D coatings (2.4%) and C25C electrolytic production (2.0%) round out the picture — a reminder that much of the claim activity around this joint sits in interface metallurgy and surface treatment rather than in the weld schedule itself.
Shares are the percentage of the 51,331 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Resistance Spot Welding of Aluminium to Steel with Eureka
This page is one run against one query. Ask Eureka your own question about resistance spot welding of aluminium to steel and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative recent filing
US20250096724A1 — Cover plate assembly and foldable cover plate
Filed by Shenzhen WKSP Power Technology and published 2025-03-20, this application claims a cover plate assembly for photovoltaic panels built from a bonding layer and a cover plate with supporting and reinforcement layers, where the supporting layer can be an aluminium alloy. It illustrates how aluminium-alloy structural layer claims continue to be filed adjacent to, rather than inside, core dissimilar-metal welding claim language.Abstract condensed from the original filing.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | EP1306454A1 | Rhenium containing protective coating protecting a product against corrosion and oxidation at high temperatur… | 989 |
| 2 | EP0486489B1 | High-temperature-resistant, corrosion-resistant coating, in particular for components of gas turbines | 851 |
| 3 | EP0412397B1 | Rhenium-containing protective coating with high corrosion and oxidation resistance | 809 |
| 4 | US5179471A | Spectrally selective mirror and method for making same | 492 |
| 5 | US4435550A | Method for polymerizing alpha -olefin | 491 |
| 6 | GB1347950A | Antiperspirant aerosol system | 393 |
| 7 | US5391517A | Process for forming copper interconnect structure | 303 |
| 8 | GB1473201A | Washing and/or bleaching compositions containing silicate cation exchangers | 281 |
| 9 | US20100041939A1 | Blood pump with micromotor | 275 |
| 10 | GB1473202A | Washing and/or bleaching compositions containing silicate cation exchangers | 252 |
Citation counts favour older records simply because they have had longer to accumulate citations inside the searched corpus — read them as a signal of influence on later filings, not as a ranking of current commercial importance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the data implies for filing strategy
Three patterns worth acting on before drafting or freedom-to-operate work in this space.
Activity has pulled back from its 2019 peak
Filings peaked at 458 in 2019 and fell from 315 in 2021 to 152 in 2024, the most recent complete year. That is a genuine contraction over a comparable three-year span, though 2025-2026 figures are still incomplete and should not yet be read as continued decline.
No single filer dominates the field
The five most active assignees together account for only 5.3% of all records, and the ten most active for 8.9%. This is a long-tail landscape where freedom-to-operate risk is distributed across many smaller filers rather than concentrated in a handful of blocking portfolios.
Alloy and coating chemistry outweighs the weld process
C22C alloy composition and C23C coating classes each draw a larger share of filings than B23K welding itself. Claim activity is weighted toward what happens at and around the interface — alloy design, coatings, electroplating — more than toward electrode force or current-schedule process claims.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to resistance spot welding of aluminium to steel, with the prior art for and against each one.
Who is filing, and where the gaps sit
The ranked leaders in this dataset span aluminium producers, coating specialists and process-electrode originators, but none of them holds a commanding share — recent-year momentum for several major names has flattened to zero.
A long tail beneath a modest lead group
The leader holds 672 records, fifth place 464, and tenth place 323 — a gentle taper rather than a cliff. With the top 10 combined at only 8.9% of all records, most of the field's filing activity sits outside the ranked leaders entirely.
Established filers have gone quiet in the most recent year
Several long-standing assignees in the ranking show zero filings in the latest year, including one name with a -100% year-on-year change. That is consistent with the broader 2021-2024 contraction rather than a sign any one company has exited the space.
Collaboration is limited and clustered
Only ten co-assignee pairs appear in the dataset, and the strongest links cluster around a small number of repeat inventor-assignee combinations. Joint filing is the exception here, not the norm.
| Assignee | Recent year | YoY |
|---|---|---|
| Corus Aluminium Walzprodukte GmbH | 0 | — |
| Moltech Invent S.A. | 0 | — |
| Norsk Hydro ASA | 0 | — |
| Alcan International Ltd. | 0 | — |
| Novelis Koblenz GmbH | 0 | — |
| Henkel KGaA | 0 | -100% |
| Pechiney Rhenalu | 0 | — |
| Siemens AG | 0 | — |
Where to take this next
The dataset points to specific follow-up work rather than a single conclusion.
Check freedom-to-operate against the long tail
With the top 10 assignees holding under 9% of records, a freedom-to-operate search here needs to cover far more than the ranked leaders — the risk is distributed.
Run a freedom-to-operate scan in EurekaWatch for the 2025-2026 publication catch-up
Because publication lags filing by roughly 18 months, the apparent decline through 2024 will partly fill in as 2025 and 2026 applications publish. Re-check the trend in a future cut before concluding the field is shrinking.
Set a monitoring alert in EurekaProbe the under-claimed process-side branches
Alloy and coating classes dominate filings; current-schedule and cover-plate insert claims are comparatively thin. That gap is worth a targeted prior-art search before drafting.
Explore white space in EurekaCommon questions about this landscape
The ranking covers 100 companies drawn from 51,331 records, with the leading assignee holding 672 records and the fifth-ranked holding 464. No single company dominates: the top 5 combined account for only 5.3% of all records in scope, and the top 10 for 8.9%. That means the field is a long-tail landscape rather than one controlled by a handful of blocking portfolios, and a competitive review should look well beyond the leading names.
Filings peaked at 458 in 2019 and, using the two most recent complete years, fell 52% from 315 in 2021 to 152 in 2024. That is a genuine contraction over a comparable period. However, figures for 2025 and 2026 are still incomplete because publication typically lags filing by around 18 months, so it is too early to call the most recent trend a continued decline.
Alloy composition (IPC class C22C) appears in 10.2% of the 51,331 records, and coating and surface deposition (C23C) in 6.5%, both ahead of welding, soldering and brazing itself (B23K) at 3.4%. Non-ferrous metal treatment, layered laminates, electroplating, coatings and electrolytic metal production each carry smaller but still notable shares. This indicates that much of the patenting activity addresses the metallurgical interface and surface treatment around the joint rather than the weld process controls alone.
Sub-areas such as cover-plate insert geometry for dissimilar stacks, cross-tension fatigue prediction, intermetallic-layer thickness control algorithms, corrosion-resistant faying-surface pre-treatment and multi-step current schedule optimisation show comparatively thin direct claim coverage relative to the dense alloy and coating classes. These sit adjacent to well-filed territory, which typically means fewer blocking claims but also thinner supporting prior art for examination. A first claim in these branches should tie a specific structural or process parameter to a measurable joint-performance outcome to distinguish it from the surrounding alloy and coating art.
Citation counts in this dataset favour older records simply because they have had more time to accumulate citations, so the most-cited entries here are not necessarily the most commercially important today. They are better read as a signal of historical influence on later filings within the searched corpus. For assessing current relevance, filing recency and IPC composition are more informative than raw citation counts alone.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.